Add RelatedIssuesService

See https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1797

app/assets/javascripts/issuable/related_issues/services/related_issues_service.js

+import Vue from 'vue';
+import vueResource from 'vue-resource';
+
+Vue.use(vueResource);
+
+class RelatedIssuesService {
+  constructor(endpoint) {
+    this.relatedIssuesResource = Vue.resource(endpoint);
+  }
+
+  // eslint-disable-next-line class-methods-use-this
+  fetchIssueInfo(endpoint) {
+    return Vue.http.get(endpoint)
+      .then(res => res.json());
+  }
+
+  fetchRelatedIssues() {
+    return this.relatedIssuesResource.get()
+      .then(res => res.json());
+  }
+
+  addRelatedIssues(newIssueReferences) {
+    return this.relatedIssuesResource.save({}, {
+      issue_references: newIssueReferences,
+    })
+      .then(res => res.json());
+  }
+
+  // eslint-disable-next-line class-methods-use-this
+  removeRelatedIssue(endpoint) {
+    return Vue.http.delete(endpoint)
+      .then(res => res.json());
+  }
+}
+
+export default RelatedIssuesService;

spec/javascripts/issuable/related_issues/services/related_issues_service_spec.js

+import _ from 'underscore';
+import Vue from 'vue';
+import RelatedIssuesService from '~/issuable/related_issues/services/related_issues_service';
+
+const issuable1 = {
+  reference: 'foo/bar#123',
+  title: 'some title',
+  path: '/foo/bar/issues/123',
+  state: 'opened',
+  destroy_relation_path: '/foo/bar/issues/123/related_issues/1',
+};
+
+describe('RelatedIssuesService', () => {
+  let service;
+
+  beforeEach(() => {
+    service = new RelatedIssuesService('');
+  });
+
+  describe('fetchIssueInfo', () => {
+    const interceptor = (request, next) => {
+      next(request.respondWith(JSON.stringify(issuable1), {
+        status: 200,
+      }));
+    };
+
+    beforeEach(() => {
+      Vue.http.interceptors.push(interceptor);
+    });
+
+    afterEach(() => {
+      Vue.http.interceptors = _.without(Vue.http.interceptors, interceptor);
+    });
+
+    it('fetch issue info', (done) => {
+      service.fetchIssueInfo('...')
+        .then((issue) => {
+          expect(issue).toEqual(issuable1);
+          done();
+        })
+        .catch((err) => {
+          done.fail(`Failed to fetch issue:\n${err}`);
+        });
+    });
+  });
+
+  describe('fetchRelatedIssues', () => {
+    const interceptor = (request, next) => {
+      next(request.respondWith(JSON.stringify([issuable1]), {
+        status: 200,
+      }));
+    };
+
+    beforeEach(() => {
+      Vue.http.interceptors.push(interceptor);
+    });
+
+    afterEach(() => {
+      Vue.http.interceptors = _.without(Vue.http.interceptors, interceptor);
+    });
+
+    it('fetch related issues', (done) => {
+      service.fetchRelatedIssues()
+        .then((relatedIssues) => {
+          expect(relatedIssues).toEqual([issuable1]);
+          done();
+        })
+        .catch((err) => {
+          done.fail(`Failed to fetch related issues:\n${err}`);
+        });
+    });
+  });
+
+  describe('addRelatedIssues', () => {
+    const interceptor = (request, next) => {
+      next(request.respondWith(JSON.stringify({
+        message: `${issuable1.reference} was successfully related`,
+        status: 'success',
+      }), {
+        status: 200,
+      }));
+    };
+
+    beforeEach(() => {
+      Vue.http.interceptors.push(interceptor);
+    });
+
+    afterEach(() => {
+      Vue.http.interceptors = _.without(Vue.http.interceptors, interceptor);
+    });
+
+    it('add related issues', (done) => {
+      service.addRelatedIssues([issuable1.reference])
+        .then((resData) => {
+          expect(resData.status).toEqual('success');
+          done();
+        })
+        .catch((err) => {
+          done.fail(`Failed to add related issues:\n${err}`);
+        });
+    });
+  });
+
+  describe('removeRelatedIssue', () => {
+    const interceptor = (request, next) => {
+      next(request.respondWith(JSON.stringify({
+        message: 'Relation was removed',
+        status: 'success',
+      }), {
+        status: 200,
+      }));
+    };
+
+    beforeEach(() => {
+      Vue.http.interceptors.push(interceptor);
+    });
+
+    afterEach(() => {
+      Vue.http.interceptors = _.without(Vue.http.interceptors, interceptor);
+    });
+
+    it('remove related issue', (done) => {
+      service.removeRelatedIssue('...')
+        .then((resData) => {
+          expect(resData.status).toEqual('success');
+          done();
+        })
+        .catch((err) => {
+          done.fail(`Failed to fetch issue:\n${err}`);
+        });
+    });
+  });
+});